Process for the manufacture of lubricating oils



Feb. 8, 1944.

RID. EVANS E'rAL.

PROCESS FOR THE MANUFACTURE OF LUBRICATING OILS Filed Sept. 2, 1941 4 Sheets-Sheet 1 g. .mul

INVENTOR BERT D. EVANS MES V. M

ONTGOMERY Feb. 8, 1944. R. D. EVANS Erm.

PROCESS FOR THE MANUFACTURE 0F LUBRICATING OILS 4 Sheets-Sheet 2 Filed Sept. 2, 1941 mw +OR INVENTOR ROBERT D. EvANs Es v MONTGOMERY BY l; 4 .l

ATTOR@ E Feb. 8, 1944.

R. D. EVANS vEI'AL 4 Sheets-Sheet 5 Filed Sept. 2, 1941 Om. n@ OQ mm Om mN ON m- O- m EIO-|03 NOSNlEOtI-QVL INVENTOR ROBERT D EVANS m E M @4 l E m M`m v A s. E l MYym B Feb. 8, 1944. R. D. r-:vANs x-:r'AL

PROCESS FOR THE MANUFACTURE OF LUBRICATING OILS Filed sept; 2, 1941 4 Sheets-Sheet 4 Om n? BO'IOO NOS NISOH- 9V.L

. INVENTOR ROBERT D. EVANS lsMES V MAONTGOMERY ATToR Y v Patented Feb. 8, 1944 PROCESS FOR THE MANUFACTURE OF LUBRICATIN G OILS Robert D. Evans, Okmulgee, Okla., and James V.

Montgomery, Edgewood, Md., assignors to Phillips Petroleum Company, a corporation of Delaware Application September Z, 1941, Serial No. 409,280

8 Claims.

The present invention relates to a process for refining mineral oils with acid and activated clay, and is more particularly concerned with the treatment of mineral oils with these materials to produce lubricating oils of greater stability and improved characteristics than heretofore attainable.

Acid and clay rening have been employed alone and in combination for the treatment of lubricating oils, and are well known for the beneficial effects which they impart thereto. Such prior methods, however, are directed mainly to treatment of waxy lube stock which results in the clay becoming completely exhausted, and therefore have proven a rather costly mode of procedure. Further methods have been proposed Which involve acid-clay treatment of de- Waxed oils which have not previously been rened to accomplish the removal of pour point depressors. These materials consist mainly of asphaltic and/ or tarry matter and when present prevent thorough dewaxing due to their adverse eifect on wax crystallization. Likewise, when the oil has not been treated specifically to remove pour point depressors, subsequent treatment with acid causes a very substantial increase in the pour point of dewaxed oil.

An object of the invention is to produce lubricating oils more highly refined and of greater stability than attainable by acid and clay refining methods heretofore. A further object is to provide a process of refining lubricating oils which is economical and elcient. Another object is to accomplish the removal of pour point depressants prior to dewaxing. A still further object is to provide a process which will result in acidfree distillates and avoid the corrosion of equipment. Another object is to provide an oil of improved color. Another object isto provide an oil of improved gravity.

The present invention provides a process which involves a primary acid treatment preferably with sulfuric acid, whereby pour point depressors are substantially removed with other impurities, followed by contact with activated clay for the adsorption of principal color body and asphaltic content and neutralization of the acid oil. This enables a very thorough dewaxing of the lube oil stock, and thereafter the oil is subjected to a further acid-stabilizing treatment. The final treatment with acid results in a stable oil unaltered by subsequent treatment and without substantial change in pour point. The latter effect is due to the removal of constituents by the primary acid treatment, which if present during dewaxing and if removed in the stabilization treatment would cause a substantial rise in pour point. The invention further contemplates the use of acidsludge from the stabilizing step for treatment of the waxy lube stock, thereby providing a substantial economy. The acid oil from the stabilization treatment is treated with contact clayjfor the removal of traces of color bodies and impurities not previously removed and neutralization of the acid oil. Clay derived from the treatment of stabilized acid oil is preferably employed in treatment of acid oil from the primary acid treat. It has been found that spent clay from ordinary plant processes, where initial contact is affected in the presence of wax, asphaltic and tarry constituents, is substantially spent and of such low efficiency that it must be either discarded or reactivated. It is a feature of this invention that fresh activated clay used to treat oil from which wax, asphaltic and other impurities have been substantially removed, is employed to neutralize waxy acid oil and remove the greater portion of the asphalt and color bodies prior to dewaxing. This clay retains sufcient activity and adsorptivity to adsorb a substantial amount of asphaltic constituents, and at the same time-neutralize the waxy acid oil derived from the primary acid contact. Dewaxed oil which has received a final stabilizing and clay contact treatment in accordance with this invention has been found to retain better stability and to be much more highly refined than oil produced by known methods. An important phase of the process is the distillation of the clay treated stabilized oil in the presence of the clay. By methods previously known, a certain amount of acid, not physically or chemically bound to the clay, remains in the oil, and an essential feature of this invention consists in flashing off this acid just prior to distillation.

Briefly, we propose to produce finished lubricating oils of improved characteristics by separating residual lube stock into an overhead waxy lube stock and residual tar by distillation at controlled temperatures, either `at atmospheric pressure or above or below atmospheric pressure, with or Without the use of steam or other diluents. The distilled waxy lube stock is then treated with partially spent sulfuric acid contained in sulfuric acid sludge formed during the further treatment of dewaxed lube stock with fresh sulfuric acid, as later described, and preferably at a temperature Within the range of from 80 to 140 F. Optionally, the Waxy acid oil may be further treated with fresh sulfuric acid, preferably 98 percent sulfuric acid. The waxy acid oil is then contacted at controlled elevated temperatures with clay obtained from the contacting of dewaxed acid oil with fresh clay, as later more fully described. The contacting step with clay is preferably carried out by multipass in furnace tubes with or without steam and/or added water at temperatures in the range of from 400 to 600 F. Other temperature ranges may be employed, but it has been found that this temperature is sufiicient to bring the activity of the partially spent clay to the desired point. As an integral part of the contacting step, acid materials not physically or chemically bound to the clay are flashed off in a clay-oil flash pot, later described in detail. The clayoil mix is then filtered and the treated waxy lube distillate is dewaxed, preferably by filter de- Waxing from solution in an acetone-benzol-toluene or similar dewaxing solvent. The dewaxed lube stock is then stabilized by treatment with fresh sulfuric acid at controlled temperatures and with either 98 percent acid or fuming 104 percent acid, or if dilution is employed,rthe treatment may be carried out at temperatures as low as F. We prefer to operate upon the undilute oil with 98 percent sulfuric acid at or near atmospheric temperature, such as from 60 to 120 F. The acid' sludge from this treatment retains a sufficient acid value for the removal of pour point depressors from waxy lube stock of relatively W viscosity in the primary treat. The dewaxed acid' oil or dewaxed acid oil solution is then contacted with fresh activated contact clay in furnace tubes at controlled elevated temperatures. A contact method may be either a singlepass or multiple-pass, with or without steam or added water, and the temperature depends upon the material being treated, the contact time and whether or not the diluents are present. Acidic materials not physically `or chemically bound to the clay vare thereupon fiashed off at elevated temperature, i. e., from 400 to 600 F., in a clayoil flash pot and the clay-oil mixture is further heated in a furnace coil or similar apparatus and charged to distillation equipment where separation is effected into an acid-free distillate, consisting ofa highly improved lube oil of relatively low viscosity and a residual, greatly improved lube oil of relatively high viscosity vcontaining clay. The distillation is vcarried out in conventional-equipment, and at controlled temperatures to avoid injury to the oil. Steam or low boiling diluents may be used to aid in the distillation, if it is carried out at atmospheric pressure. Vacuum distillation is advantageous, either with or withoutsteam or other diluent; however, we prefer to employ dry ash vacuum distillation.

The residual lube oil is filtered to remove clay, producing a highly improved acid-free lube oil of relatively high viscosity. The distillate and residual lube oil are highly improved, stable lube oils, and may be used separately or blended in any desired proportions. The clay from the latter step-remains approximately 50 percent efiicient, and may be employed in treatment of fresh waxy lube stock for the removal of pour point depressors, other impurities, and neutralization of the oil.

The contacting of the waxy acid oil with clay 5 obtained from treatment of dewaxed oil is sufficient to effect substantial neutralization of the acid content of the oil, thereby avoiding the use of neutralizing agents commonly employed, such as caustic, ammonia, lime and the like, which promote the formation of emulsions and production of soluble soaps which are difficult to remove from the oil. The clay from the secondary clay contact treatment is effective to the desired degree when used to contact the oil in furnace tubes at elevated temperatures, whereas mere filtration of the oil through a cake of partially spent clay f does not develop the necessary activity. We have found, however, that oil so treated retains a small amount of acid not physically or chemically bound to the clay, which it is difficult or impossible to render inactive irregardless of the quantity of clay employed. The presence of this acid not physically or chemically bound to the clay is objectionable, particularly in the oil following the second contact stage with fresh clay which will result in acid distillates. as well as promote corrosion of equipment. In accordance with this invention, we flash off this acid not physically or chemically bound to the clay at elevated temperatures, i. e., from 400 to 600 F. in the presence of the clay, and prior to distillation in the second stage,

The stabilization with fresh acid on dewaxed oil produces a highly improved lube oil and is 35 much more effective as a stabilization measure than when acid treatment is made in the presence of Wax. This treatment is likewise economical since the expensive treating agent is used on the lube stock only and after asphalt and wax have been removed. This final stabilization step is sufficiently late in the refining process to lbe practically unaffected by subsequent refining steps and the oil so treated remains stable even under the infiuence of relatively high temperae tures. Likewise, a substantial rise in pour point of the dewaxed oil is not experienced, due to the fact that pour point depressors were removed prior to dewaxing. The nal clay contact with new clay effects neutralization of the acid oil and is highly effective to accomplish the removal of color-forming materials and traces of residual impurities, thereby producing a highly stable and refined lubricating oil. Contacting the oil with clay removes all acid residues, both with the aid of steam and consequent removal from the flash pot, and by chemical and physical action within and upon the clay particles, causing said material to be bound to and adsorbed by the clay and thereby removed from the oil. This allows distillation to take place without corrosion of equipment, and without the production of acid lube distillates.

Figures 1 and 2 illustrate diagrammatically an apparatus suitable for carrying out the process of this invention, Figure 2 being acontinuatlon of Figure l. Figure 3l is a graph illustrating the comparative efficiencies of new andused clays on acid oil from 71 S. U. V. at 210 F., vacuum distillate. Figure 4 is also a graph illustrating the comparative efficiencies of new and used clays on acid oil from a 102 S. U. V. at 210 F. blend of 80% pipe still residuum and 20% vacuum distillate.

storage tank i is flowed through line 2 to furnace 3 whence it is withdrawn through line 4 to still 5. Furnace 3 and still 5 may be the well known pipe still-bubble tower combination, or may be any other conventional distillation unit used in the art to separate crude mineral oil into overhead distillates and residual lube stocks. Steam from line 6 may be introduced into still 5 to aid in distillation. Overhead products are withdrawn as through line l, and the residual lube stock of desired flash and viscosity is withdrawn through line 8 to storage tank 9. The residual lube stock from storage tank S is flowed through line I to furnace il and thence withdrawn through line l2 to still i3. Still i3 may be a conventional atmospheric still where distillation is effected by use of steam admitted through line M, or may be a Vacuum still where either steam or low boiling hydrocarbon is admitted through line lli to aid in distillation. We prefer to use dry flash vacuum distillation, wherein line ill is omitted. In the case of vacuum distillation, the reduction in pressure is efected by means of mechanical vacuum pumps or by steam jet ejectors, not shown. If desired, still i3 may contain reboiler tubes, not shown, through which heated liquid is circulated to assist in stripping the tarry residue. In any case the distillation steps in stills 5 and I3 may be carried out in conventional equipment, and the method of distillation is not considered a part of our invention. From still i3, the asphaltic residue, or tar, is withdrawn through line I5 to storage, not shown. Waxy lube distillate is taken overhead from still I3 through line I6, through condensing equipment, not shown, and to storage tank l '1, thence to acid treating equipment iii through line i3. If desired, residual lube Stock from storage tank 9 may be owed directly through line 2G to acid treating equipment i9. Ii desirable, the oil charge to acid treating equipment i 9 may be a combination of waxy lube distillate from still i3 and waxy residual lube stock from tank S. Acid sludge is admitted to acid treating equipment i9 through line 2i from sludge charge pot 22. Acid treating equipment it may be conventional acid treating equipment, either batch or continuous. If desired, acid treatment may be carried out in solution, in which case naphtha or other suitable diluent may be introduced through line 23. In case the diluent is propane or other similar material of high vapor pressure, apparatus I9 must be o suitable material and construction to permit of usage at above atmospheric pressure. The acid oil, or acid oil solution, is withdrawn from treater i9 through line 24 to acid treating equipment 25. This equipment may be similar in design and operation to equipment i9, or may be other conventional acid treating equipment. New acid is admitted to through line 2l, from storage not shown. Acid sludge from l is withdrawn through line 2S and thence through line 3G to storage not shown, Acid sludge from 25 is withdrawn through line 28 and thence may be combined with sludge from line 26 and flowed to storage through line 3S, or when and as desired, may be flowed through line 29 to sludge charge pot 22. If desired, gas oil or other suitable diluent may be added to the acid sludge in line 3E from line 3i, to impart desired fluidity to the sludge to permit pumping and other handling. Acid-oil, or acidoil solution from 25 is withdrawn through line 32 to storage tank 33, and thence to line 3d and clay-mix tank 35 to which clay from the stabilization treatment is added through line 36. If desired, water may be added to line 36 through line 3l from source not shown. 'I'he clay-oil mix in may be obtained in conventional manner. We prefer to use mechanical agitation as by recirculating pumps or by motor driven stirrer. The clay-oil mix from 35 is owed through line 38 to furnace 39 and thence through line 40 to flash pot 4|. In ilash pot lll, volatile acid compounds, steam, and low boiling diluent (if present) are withdrawn through line 4t2. If desired, steam or low boiling diluentv may be added to iiash pot M through line dil-A. The volatile acidic materials, steam and/or low boiling diluent from line 42 are flowed into tower d3 to which cooling water or other cooling and absorption medium is admitted through line 45. Non-condensed vapors are withdrawn through line IM. If propane or other similar low boiling diluent has been used, it is withdrawn through line 4d. Water, acid materials, and any light lube oil fractions which may have been distilled from flash pot lil are condensed in tower i3 and flowed through line 45 to separator il whence mineral oils are withdrawn through line i8 to storage not shown and water and acidic materials are withdrawn through line i9 to discard. 'ii-Ict -clay-oil mix from flash pot fil is withdrawn through line 5D, A portion is recirculated to furnace 39 through lline 5l and the balance is withdrawn through line 52 to clay-oil surge tank 53. The temperature of the above described clay-contacting process is controlled as desired, in furnace til. We prefer to operate in the approximate range of 40) to 600 F., but other temperatures are permissible and may at times be desirable. When clay from the stabilization treatment is employed, this procedure is found preferable. The contacting in furnace 3S may be singlepass, or multiple-pass, as we have described. The clay-oil mix from surge pot 5e is flowed through line 51S to lter equipment Ii desired, diluent may be added through line Filter apparatus 55 may be any conventional iilter equipment, such as the well known Oliver rotary filter, or the Sweetland filter press type, or other similar equipment. Spent clay is withdrawn from 55 through line 5l, and may be discarded, re-claimed, or processed to recover contained oil, as desired. Filtered oil, or hltered oil solution, is withdrawn through line 5S to dewaxing equipment 59. DewaXing may be by conventional method. We prefer to use filter dewaXing with suitable solvent as propane, acetone-benzoltoluene, etc. The method and act of dewaxing are known art, however, the point in the entire refining process at which dewaxing is carried out is highly critical in the present invention. Petrolatum or wax from dewaxing equipment 59 is withdrawn through .line tu to storage not shown, and the dewaXed oil from 59 .is withdrawn through line 6i to storage tank t2. A draw-ofi @d is shown for low grade lube oils which may be used for blending purposes. The dewaxed lube oil stock is withdrawn from tank t2 through line t3 and thence through line S5 to stabilization acid treating equipment 66. New acid is added to Sli through line 5l' from source not shown. Ii desired, propane, low boiling naphtha, or other suitable diluent may be added to S5 through line SS from source not shown. Acid-treating equipment t6 may be conventional acid-treating equipment, either batch or continuous, and may or may not be carried out in solution in low boiling diluent. The temperature may be controlled, as desired. We prefer to treat undiluted lube stock at approximately 60 to 120 F., but treatment may be carried out in solution in propane or other diluent, at sub-atmospheric temperatures as at F., or lower. Acid sludge, containing valuable partially spent acid, is withdrawn from 66 through line 68 to storage tank 1|), and thence through line 1| to sludge charge pot 22 for use in treating waxy lube stock in I9, as previously described. If desired, the acid treatment in 66 may be preceded by separation of the dewaxed lube stock into fractions of different viscosity by distillation, or propane fractionation in conventional manner in equipment not shown. Acid-oil, 0r acidoil solution, from 56 is withdrawn through line 12 to storage tank 13, and thence through line 14 to clay-mix tank 15. New activated contact clay, such as Filtrol contact clay is added to 15 through line 16. If desired, water is added to line 15 through line 11. Agitation may be by conventional means. We prefer to use recirculating pumps or motor driven stirrer. The clay-oil mix from 15 is owed through line 18 to furnace 19 and thence through line 80 to ash pot 8|. In flash pot 8|, volatile acid compounds, steam and low boiling diluent, if present, are withdrawn through line 82. If desired, steam or low boiling diluent may be added to flash pot 8| through line 8-A. The volatile acidic compounds, steam and/ or low boiling diluent from line 82 are owed into tower 83 to which cooling water` or other cooling and absorption medium is admitted through line 85. Non-condensed vapors are withdrawn through line 84. If propane or other similar low boiling diluent has been used, it is Withdrawn through line 84. Water, acidic materials and any light lube oil fractions which may have been distilled from flash pot 8| are condensed in tower 83 and flowed through line 86 to separator 81 whence mineral oils are withdrawn through line 88 to storage not shown, and water and acidic materials are withdrawn through line 89 to discard. Hot clay-oil mix from ash pot 8| is withdrawn through line 90. A portion is recirculated to furnace 19 through line 9|, and the balance is withdrawn through line 92 to heating coil 93. Heating coil 93 may be a part of the furnace 19, or, if desired, may be in a separate furnace. From heating coil 93 the hot clay-oil mix is withdrawn through line 94 to still 95. The temperature of the above clay-contacting process is controlled as desired in furnace 19. We prefer to operate in the approximate range of 400 to 600 F., but other temperatures are permissible and may at times be desirable. The contacting in furnace 19 may be single-pass, or multiplepass, as we have described. In any case, the method in flash pot 8| is an essential feature for in this manner we avoid the presence of acidic and corrosive materials in still 95. `The temperature in heating coil 93 is controlled in the necessary range to effect the desired distillation in still 95. Still 95 may be an atmospheric still of conventional design where distillation is effected by the use of steam admitted through line Sil-A, or may be a vacuum still. We prefer to use dry flash vacuum distillation, wherein line 94-A is omitted. In the case of vacuum distillation, the reduction in pressure is effected by means of mechanical pumps or by steam jet ejectors, not shown. If desired, still 95 may contain reboiler tubes, not shown, through which heated liquid is circulated to assist in stripping the residual oil. Distillation of the oil from which volatile acidic materials have been flashed oi previously in the presence of claypromotes better adsorption of the impurities by the clay, and avoids acid distillates. From still 95, the distillate consisting of highly improved lube oil of relatively low viscosity is withdrawn through line 96, and thence through condensing and cooling equipment and separating equipment if steam has been used, not shown, and on to storage. The residual oil and clay is withdrawn from still 95 through line 91 and thence through line 98 to clay-oil surge pot 99. The clay-oil mix from surge pot 99 is fiowed through line |00 to filter equipment |0|. Filter apparatus ||J| may be any conventional filter equipment, such as the well known Oliver rotary lter, or the Sweetland filter press type, 0r similar equipment. Clay is withdrawn from through line |92 and thence is recirculated to clay-oil mix tank 35, as previously described. If desired, acid oil from acid oil storage tank 33 may be added to the clay from the stabilization treatment in line |02 and thence is recirculated to clay-oil mix tank 35, as previously described. Also, if desired, acid oil from acid oil storage tank 33 may be added to the clay from the stabilization treatment in line |02 through line |93 to impart necessary fluidity for pumping. Filtered oil, consisting of highly improved lube oil of relatively high viscosity is withdrawn from ||l| through |64 to storage, not shown.

If desired, wax-free oil from storage tank 62 may be flowed through line 63 and 'I4-A, direct to clay-oil mix tank 15, thus omitting the acid stabilization step. In some cases, both acid stabilization and clay-contacting may be omitted,

35 in which case wax-free oil from storage tank 62 is withdrawn through lines 63, Sil-A, and 92 to heating coil 93, and thence to fractionating still 95. Unless previously refined, oils sotreated are of inferior quality.

Clay-oil mix from heating coil 93 may be flowed through lines 94, 91-A, 91 and 98, direct to clayoil surge pot 99, when fractionation is not necessary In addition to the highly improved oils which result from the specific mode of treatment in accordance with this invention, substantial economies are effected, first by the use of acid sludge from the stabilization step for the treatment of the waxy lube which serves to recover any valuable lube stock contained in the sludge from those treating steps and likewise permits the full utilization of the acid. It has been found, for instance, that this sludge possesses an acid value equivalent to about 40 percent of the weight of the entire amount of new acid employed in the stabilization step. Thus, the maximum amount of fresh acid is used in the final treatment Where it is most effective and also obviates waste of useful acid in the sludge.

lThe use of clay from the stabilization treatment for contacting waxy acid oil under the inuence of heat is a convenient and economical method for effecting neutralization. Of course, new clay or clay derived from other sources or employed in contacting partially refined oils having the required activity may be employed for this purpose, the specific mode of treatment being responsible for the improved lube oil herein disclosed. The clay obtained by this process has about 50 percent of the efciency of new clay and contains an appreciable quantity of useful oil adsorbed in the secondary treatment when removed from the filter. By using this clay to contact waxy acid oil this oil is recovered, we believe, by `displacen'ient from the clay by selective adsorption of resinous and asphaltic materials present in the waxy acid oil. In addition, excessive and unnecessary refining of by-products, such as wax, is avoided since the treatment of the waxy lube stock is carefully controlled so as to remove only asphalt, tar and other undesirable materials, such as pour point depressors, so that these materials are not present to contaminate the wax during dewaxing.

Figures 3 and 4 illustrate graphically the advantages and economies derived in this process by the use of clay from the stabilization treatment on waxy acid oil in the initial contact stage. The pounds of clay per barrel of oil are plotted against a Tag-Robinson color scale.

Referring to Figure 3, the comparative efciencies of 'new and used clays on acid oil from 71 S. U. V. 210 F. vacuum distillate are compared. The line marked New Clay shows the Tag-Robinson colors that can be obtained by contacting the vacuum distillate with various amounts of new AFiltrol clay. Note that eight pounds of new clay per 'barrel of oil will give 5 Tag-Robinson color. To compare efficiencies, the line 5 Tag-Robinson color is used for the basis of comparison and eight pounds per barrel of new Filtrol clay is arbitrarily taken as 100% efficient. It takes twelve pounds per barrel of used clay from a stabilization treatment of 366 S. U. V. 100 F. dewaxed neutral oil to make 5 Tag-Robinson color on acid oil from 71 S. U. V. 210 F. vacuum distillate. As the neutral oil was highly rened before it was contacted with the clay, the clay still retained 67 percent of the efficiency of new clay when it was reused in contacting vacuum distillate.

Using clay from' a stabilization treatment of dewaxed 71 S. U. V. 210 F. vacuum distillate, it takes 17 pounds of 'the used clay per barrel of oil to make 5 Tag-Robinson color. This is an eiciency `of 47 percent. The efficiency is lower than that of the clay from `stabilizing neutral oil because the dewaxed '71 viscosity vacuum distillate is a slightly heavier oil than the neutral oil and it is not quite so highly rened. When clay from the `treatment of a waxy 102 S. U. V. 210 F. stock is employed, it takes 42.5 pounds of the used clay per barrel of oil to make 5 Tag-Robinson color. This is an efciency of 19 percent. The stock originally treated with this clay is heavier and less highly refined than either of the other two.

From this graph, four general conclusions can be drawn:

1. The more highly rened an oil is when contacted with clay, the greater is the elilciency of the used clay.

2. The lower the viscosity of an oil when it is contacted with clay, the greater is the, efciency of the used clay.

3. A spent clay from a stabilization treatment of a dewaxed distillate is substantially more efcient than the one which has resulted from the treatment of a waxy distillate as in usual plant operation.

4. Considerable economies 4are effected inasmuch as much less clay is'necessary to obtain a given Tag-Robinson color using new clay 'for treating dewaxed oil and thereafter for treatment of waxy acid oil.

Referring to Figure 4, the comparative'eciencies of new-and used clays on acid oil from a 102 S. U. V. y@l 210 F.. blend of 80% pipe still residuum :and 20%"va'cuum -distillate are compared. Asbefore, the line marked New -Clay shows the colors that `can be obtained .by contacting the blend with new clay. This has a darker obtain the same color of contacted oil. This blend, for example, requires 15 pounds of new clay per barrel of oil uto make 5 Tag-Robinson color, whereas the vacuum distillate requires only 8 pounds of new clay per barrel of oil. To compare efficiencies on this graph, use the line 2 Tag-Robinson color. Seven pounds of new clay per barrel of koil are required to make 2y .Tag- Robinson color; this is arbitrarily taken as 100% eflicient.

Using clay from the stabilization treatment of 330 S. U. V. @l 100 F. dewaxedneutral oil, 131/2 pounds of used clay per barrel of oil are vre'- quired to make 2 Tag-Robinson color. This vis an efficiency of about '52 percent.

Using clay from th'e contacting of a heavier, less highly rened oil, a waxy 102 S. U. V. 210 F. stock, requires 23 pounds of used clay per-barrel of oil to make 2 Tag-Robinson color.

`This is'an eciency of about 30 percent.

This graph confirms the general conclusions Adrawn from Figure 3 in demonstration of economies aiorded by the present invention.

The following example of the operation of our process is cited, al1 yields being based on the original crude oil.

. EXAMPLE I Mixed-base crude oil from the Oklahoma City eld in the Mid-Continent area was charged to atmospheric still 5 at a temperature of '775 F., where it Was reduced, with steam, to a 35% yield of a residual lube stock of Saybolt Universal viscosity 210 F. This residual stock was vdry ash vacuum distilled in still `I3 to a 29% yield of waxy lube stock distillate 71 S. U. V. 210 F. This waxy stock was batch treated at 130 F., in agitator I0, with 18# oflpartially spent acid per `barrel of waxy oil. This partially .spent acid was 4,contained in sludge withdrawn from agitator 66.

The 27% yield of acid oil from agitator i9 was charged to batch agitator 25 where it was treated at 130 F. with 10# of fresh 98% sulfuric acid per barrel of original, waxy oil (to l0). The 25.5% yield of 66.5 S. U. V. acid oil from agitator 25 was contacted by multiple-pass at 500 F. in furnace 39 with 11.6 pounds of clay per barrel of acid oil. The contact time was 50 minutes, with added steam. This clay was' obtained from filter IUI. The clay-oil mix was withdrawn through 52, and surge pot 53 and filtered hot, without dilution, in filter apparatus 55. There was no de crease in oil volume at this point since the clay from IOI was already saturatedwith oil which was displaced by asphalting materials and color bodies adsorbed during the contact period in furnace 39. The 25.5% yield of 67 S. U. V. contacted waxy oil was lter dewaxed at 10 F. with acetone-benzene-toluene solution in dewaxing apparatus 59. A 21% yield of dewaxed lube stock of 74 S. U. V. C@ 210 F. and 0 F. pour and-cloud point was secured. The dewaxed lube stockv was batch acid treated at F., without dilution, in acid agitator S6, with 25# of fresh 98% sulfuric acid per barrel of dewaxed oil. A 19.8% yield of 73 S, U. V. 210 F. acid oil was obtained. The acid sludge yfrom 56,-containing part-ially'spent acid, was charged toysludg charge pot'22 for reuse irl treating waxy-lube ydistillat` as i-cles'cribed The acid oil from 66,'- vasctacted bt'fmmultiple-` pass at 500 F. in furnace 19 with 15# of new Super Filtrol contact clay per barrel of acid oil. Contact time was 20 minutes, with steam and added water. 'Ihe clay-oil mix was withdrawn through line 92, heating coil 93 and line 94 to dry flash vacuum still 95. A 11.5% yield of highly improved lube oil of 50 S. U. V. 210 F. was distilled overhead. The residual oil and clay from 95 was filtered hot, Without dilution, in Inl. A 7.7% yield of highly improved lube oil of 165 S. U. V. @l 210 F. was secured. The clay from l| was recirculated to clay-oil mix tank 35 where it was used to treat waxy acid oil from agitator 25. A portion of the clay-oil mix from heating coil 93 was withdrawn directly to the clay-oil surge pot 99 and thence to clay lter IUI. By this method a 19.2% yield of highly improved lube oil of l1 S. U. V. 210 F. was secured.

Properties of the oils from the various treating stages are shown below in Table I.

TABLE I TABLE III Comparative tests on SAE lube oils as prepared by special process vs. oils prepared by conventional acz'd and clay refining Special Conventional A. E S. A. E. 20

A. P. I. gravity 29.1 27. 3 Flash ,440 420 Fir 500 480 S. U V. 210 F 52 52 A. S T. M. color 13/4 3% Ramsbottom carbon residue 0. 073 0. 153 Indiana oxidation test:

Hours to 10 nig. sludge 30 20 Hours to 100 mg. sludge 106 52 Increase 1n viscosity at 50 hrs per cent.. 7 12 O. D. color stability:

Original O. D. color 5. 2 58 Color after heating 4 hrs. 302 F. 12. 9 108 Underwood test (results on used oil):

Naphtha insoluble per cent.. 450 792 Chloroform soluble. o 393 760 Spray chamber deposi (1) 1 Stain, no deposit. I Little soft sludge.

Properties of intermediate and finished lube oils produced by special acid and clay rejining process Yield on A P I S. U. V Product crule gr'avi'ty @10 Flash C. C. R. Color Pour Cloud Percent .F. F. F. Okla. City'crude oil 100 5 Residual lube stock from still 5 I gg 2 450 400 Lov.--

Waxy lube distillate from still 13..-. Acid-oil from agt. 19 Acid-oil from agt. 25...-. Contacted oil from filter 5 Wax-free oil from dewaxer 59 Acid-oil from egt.

2% A.S.T. M 5 5 The following table illustrates the comparative acid and clay requirements for lube oils processed vin accordance with this invention compared to 'requirements for conventionally refined lube oils.

TABLE II Comparative acid and clay requirements ,for specially processed lube oils vs. conventionally refined lube oils ORIGINAL VACUUM DISTILLATE FROM OKLA.. CITY REDUCED CRUDE S. U. V, 210 F 'l1 Yield on crude per cent-- 29 Conventional refining process Special (vacuum distilrefining late, acid treated, process clay contacted,

dewaxed) Acid used per bbl. finished oil pounds.. 42. 425 43. 2 58. 5 Clay used per bbl. finished oil. 15. 22. 5 22. 5 Finished lube oil yield, percent on crude 19. 2 20. 3 19. 8 Tests:

A. P. I. gravity 26. 6 20. 2 26. 6 Flash F 465 430 440 F 545 515 520 S U V. 210 F 71 66.5 66. 5 25 3 25 A. S. T. M. color. 2% 3% 3 Indiana oxidation test at 341 F:

Hours to 10 mg. sludge 52 30 35 Hours to 100 mg. sludge S7 65 86 Increase in viscosity at hours percent.. 8 16 13. 5

The table below illustrates comparative tests on SAE 20 lube oils prepared in accordance with this invention compared with oils prepared by conventimal .acid andclay refining.

In order to demonstrate the advantages of the present process over conventional acid and clay refining, the following example is given in which lube oil specially processed in accordance with this invention is compared with oil rened by ordinary plant process.

, EXAMPLE II A lube oil is produced by ordinary plant operation as follows: A blend of pipe still residuum and 20% vacuum distillate is charged to the acid agitators. It is given two treats with 98% sulfuric acid. The acid oil is mixed with Super-Filtrol clay and 1 to 3% Water added. The m1xture is charged to the oil heater and. contacted at 525 F. to 550 F. At this temperature, the water and acid vapors ash olf in the evaporator. The contacted oil is diluted 50% with naphtha and the solution run through Sweetland presses to remove the clay. The solution is further diluted to 36% oil and chilled at a sloW rate to 44 F. It is then centrifuged to remove wax. The solution is charged to a still, and the naphtha is recovered. -At the same time, the wax-free oil is fractionated to neutral oil and S. U. V. 210 F. bright stock. This method hereafter will be referred to as present plant operation.

A blend of 80% pipe still residuum and 20% vacuum distillate was specially processed in accordance with the present invention as follows: This blend was treated with acid sludge from the stabilization of wax-free oil, and then given a second acid treat using fresh 98% acid. The waxy acid oil was neutralized by contacting with clay from the stabilization treatment of wax-free oil. Acid was flashed off and the waxy contacted oil was solvent dewaxed and wax-free oil recovered. The Wax-free cil was stabilized by treating with 98% acid, and contacted with clay. Acid was flashed oir and the oil was fractionated in the presence of the clay into a neutral oil and bottoms of 125 S. U. V. 210 F. bright stock. The clay was filtered from the bottoms and saved for neutralization purposes in the primary treatment. In the ensuing table, oil produced by this process is designated as case I.

A variation of the process was carried out in the same manner as in case I, with the exception that the rst acid treat using acid sludge from the stabilization of wax-free oil was omitted. Before dewaxing, the oil was given only one acid treat and that with 98% acid.y This method will hereafter be referred to in the table as case II.

The following table gives the laboratory tests on the finished neutral oils and bright stocks made by the foregoing three methods.

TABLE IV Specially Specially Presggflant processed processed case I case II Neu- Nen- Neii- Bright Bright Bright tall stock tl stock ETSI stock Nil 23 Nil Nil 78 Nil 144 51.8 152 50.8 143 210 F. Percent inl0 18 9.5 12 10 13 crease. 90 hr. S. U. V. 55.1 185 55.1 178 54. 4 169 210 F. Percent in- 18 51 16 31 18 -35 crease.

A number of outstanding improvements in oils specially processed in accordance with this invention over present plant oils shown in the table are as follows:

1. Oxidation stability of both neutral oil and bright stock, as measured by the Indiana oxidation test, shows much improvement.

2. The color of the finished oil is very light and is much better than present oils.

3. Conradson carbon residue of the oils is reduced.

4. An oil of improved gravity is obtained.

The material costs of proposed process, case I, were practically the same as for present plant operation. Proposed process, case II, yielded oils nearly identical with those yielded by proposed progess, case I, but at a slightly lower material cos The strength and quantity of acid necessary in the primary acid contact depends principally on the viscosity of the original oil under treatment. In the case of relatively light, low viscosity oils, it is ordinarily sufiicient to treat with sludge acid alone, while slightly heavier oils require a further light treatment with full strength acid. Heavier oils of intermediate viscosity are best treated by a single treatment with full strength acid, whereas, heavy oils of relatively high viscosity will ordinarily require a double treatment with full strength fresh acid.

. It is tlius apparent that lubricating oils produced in accordance with this invention are of highly improved characteristics over those produced by conventional methods.v These results are likewise obtained without sacrifice of eiiiciency and with improvement in economy.

We claim:

1. A method of refining lubricating oils which comprises treating wax containing lubricating oil stock with acid and separating acid sludge therefrom, contacting the resultant waxy acid oil with clay and ilashing off acid not physicallyor chemically bound to the clay in the oil, dewaxing to desired pour characteristics, acid-stabilizing the dewaxed stock, treating the separated acid oil with activated clay, flashing olf acid not physically or chemically bound to the clay in the oil and distlling the saine in the presence of the clay to recover an acid-free highly improved lubricating oil.

2. A process of refining lubricating oils wherein wax containing oils are subjected to acid and clay contact before and after dewaxing, which comprises treating the oil with acid, contacting the resultant waxy acid oil with partially spent activated clay derived from the treatment of dewaxed oil with fresh clay, dewaxing said oil to desired pour characteristics, acid-stabilizing the dewaxed stock and treating the separated acid oil with fresh activated clay for the recovery of a highly refined lubricating oil.

3. A process for the rening of lubricating oils wherein wax containing oils are subjected to acid and clay contact before and after dewaxing, which comprises treating the oil with acid of sufcient strength to remove pour point depressants, contacting the resultant waxy acid cil with partially spent activated clay obtained from the subsequent contact of dewaxed oil with fresh clay, and dewaxing the separated neutralized oil to desired pour characteristics, acid-stabilizing the dewaxed stock, treating the separated acid oil with fresh activated clay, and recovering highly refined lubricating oil.

4. A process for the refining of lubricating oils wherein wax containing oils are subjected to acid and clay contact before and after dewaxing, which comprises treating the oil with acid of suicient strength to remove pour point depressants, contacting the resultant waxy acid oil with partially spent activated clay obtained from the subsequent contact of dewaxed oil with fresh clay, and dewaxing the separated neutralized oil to desired pour characteristics, acid-stabilizing the dewaxed stock, treating the separated acid oil with fresh activated clay, flashing olf acid not physically or chemically bound to the clay in the oil, thereafter distilling the oil in the presence of the clay and recovering an acid-free highly rened lubricating oil,

5. In a process for the refining of lubricating oils wherein said oils are subjected to acid contact followed by clay contact both before and after dewaxing, the step of utilizing clay which has been contacted with said oil subsequent to dewaxing for contact with said oil prior to dewaxing thereof.

6. A process according to claim 5 wherein the acid with which the oil is contacted is sulfuric acid and in which acid sludge resulting from treatment subsequent to dewaxing is contacted with said oil prior to dewaxing.

7. A process for producing stable lubricating oils of a relatively high degree of purity which comprises substantially removing pour point depressants from wax containing oil by treatment with acid prior to dewaxing, separating acid sludge therefrom, contacting the resultant waxy acid oil with activated clay, and dewaxing to desired pour characteristics, acid stabilizing the dewaxed stock, treating the separated acid oil with activated clay and recovering highly rened 1ubricating oil.

8. A process for producing stable lubricating oils of a relatively high degree of purity which comprises removing pour point depressants from wax containing lubricating oil by treatment with sulfuric acid prior to dewaxing, separating acid sludge therefrom, contacting the resultant waxy acid oil with activated clay and dewaxing the same to the desired pour characteristics, acid stabilizing the dewaxed stock with sulfuric acid, treating the separated acid cil With activated clay, and recovering acid free rened lubricating oil.

' ROBERT D. EVANS.

JAMES V. MONTGOMERY. 

